In Chrome this results in a warning: Resource interpreted as Document but transferred with MIME type application/json.

In FireFox this results in a file download.

Conclusion: I have to change/set the Accept-header to application/json

Sencha's documentation sais it has a headers parameter, but I've tested and for fileupload it does not work. A comment said it's not supported. (found same result in another thread)

Any suggestions to get rid of the file download/ set the right Accept-header... It doesn't have to be a ExtJs sollution. If you can give me a plain javaScript solution for setting the accept header on a file upload form, I can probably mold it into the sencha framework.

Not shure if it uses iframe but I guess so..(otherwise my page would have to refresh..) this is helpfull.. I'll try the first. The second isn't an option. I have to support IE7 and up & FF 3.6 and up.
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VDPNov 12 '12 at 14:22